1. Field of the Invention
The present invention relates to an electric charging system that connects an electric charger and an electric vehicle via a charging cable and charges an electric storage device mounted on the electric vehicle.
2. Description of the Related Art
In recent years, electric vehicles that are equipped with an electric motor for propulsion have been under development. The electric vehicle is equipped with an electric storage device such as battery. Upon charging the electric storage device, a charging cable extending from an electric charger is connected to a charging port of the electric vehicle (see, for example, Japanese Unexamined Patent Application Publication No. 2009-83670). Furthermore, in the field of hybrid electric vehicles that are equipped with an engine and an electric motor for propulsion, so called a plug-in type vehicle is under development whose electric storage device can be charged with an electric charger.
Since supply power from the electric charger to the electric vehicle has a high voltage and a high capacity, it is necessary to monitor an insulation failure, a breaking of the charging cable and the like in order to prevent electric leakage or the like and secure safety upon charging. Examples of the monitoring method of the insulation failure and the like includes the comparison of a supply voltage of the electric charger and a receiving voltage of the electric vehicle and the comparison of a supply current of the electric charger and a receiving current of the electric vehicle. If there is a large difference between the supply voltage and the receiving voltage or between the supply current and the receiving current, there is a possibility that electric power flows into a system other than the electric vehicle, and thus it is determined that there occurs an insulation failure or the like.
Upon the detection of an insulation failure or the like, voltage data and current data output by a voltage sensor and a current sensor are used. When these data are used, it is common to eliminate noise effects by applying a filtering process such moving averaging and weighted moving averaging. However, there is a time lag in the filtered voltage data or the filtered current data, a simple comparison of the voltage data or the like between the electric charger and the electric vehicle may cause an erroneous determination of an insulation failure or the like. In other words, if there is a time lag between the electric charger and the electric vehicle, but the data thereof are not synchronized, there may be a big difference in the data between the electric charger and the electric vehicle although no insulation failure or the like occurs, or a difference may not be observed in the data between the electric charger and the electric vehicle although there occurs an insulation failure or the like.